I can run Flight Simulator X on decent settings with a decent framrate. Will i be able to run Fallout 3 with a decent framerate on low or medium settings?

My specs are
Nvidia Geforce 6150 Le
AMD athlon 64 dual core 4600+
4 gb ram
Windows 7

I know its terrible but i anm building a PC over the summer for l 1000 dollars and it will be amazing.

I had a similar system until i updated my video card and you should be able to play it on the lowest settings at about 10-15 fps and it's not really going to handle big battles well or any time when alot is going on.

Aside from the graphics card, you actually have a better PC than I do. (!)

Yeah, over the summer I also hope to build my own gaming rig... it svcks trying to work with 3D graphics on a PC that can hardly handle a pixel-shaded, 800x600 window with some simple particles flying around what is otherwise just a moderately complex scene! Once you get a taste of a fluid scene rendering at an unflinching 60 FPS, you just can't go back.